16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
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Inoculation affects nitrogen balances of composts and growth, yield and microflora of Phaseolus beans

Sangakkara, U.R.[1], Weerasekera, D.N., Attanayake, K.B., Attanayake, A MU.

Key words: Compost, Inoculation, Effective Microorganisms, Quality, Crop growth,

Abstract

The impact of organic matter and two types of inoculums on composting and subsequent growth of common beans was evaluated under tropical field conditions.The composts were made of commonly available organic matter with different C:N ratios, and inoculums consisting of cattle manure slurry, Effective Micro organisms or a mixture of both were added. The mixture of cattle manure and Effective Microorganisms increased N availability and reduced C: N ratios of compost thanwhen applied individually. Legume green matter enhanced compost qualityand growth yields. The nodulation and mycorrhizal populations of roots of beans were increased by a mixture of inoculums and using diverse materials in the compost. The usefulness of inoculums such as EM, which is available in all continents is presented on the basis of this study.

Introduction

Composting is a very common source of manures in organic farming due to the non use of cropping land for its production and the possibility of using different sources as its components (Diaz, 2007). The application of partiallydecomposed material also helps providing nutrients more rapidly, while long term experiments show its benefits in producing high yields in organic farming (Herencia et al, 2007).

Composing requires inoculation and is carried out using animal manures, old compost or forest soils (Diaz, 2007). Many inoculants have been developed and Effective Microorganisms (EM), consisting of Lactic acid bacteria, yeast and phototrophic bacteria in a mixture maintained at a low pH has proven to be useful for compost (Jenkins and Daly, 2005), although Mupondi et al (2006) report its non effectiveness when compared to feedstock materials in composting pine bark, which has a high C:N ratio.Thus, studies determined the impact of EM and feedstock material (cattle manure) used individually or in combination on nitrogen (N) and C:N ratios of compost made with green manures, weedand straw, which are common material in the tropics and the impact of these composts on growth, root microbes and yields of common beans (Phaseolus vulgaris L), as N is the mostdifficult nutrient to manage in organic farming (Gaskell and Smith, 2007).

Materials and methods

Experiments were carried at the University of Peradeniya, Sri Lanka from January – May, 2006. The compost piles were made with equal parts of rice straw, leaves of Gliricidia sepium, Tithonia diversifolia and common weeds, in equal proportions (1 kg fresh material) Four replicates of each pile were made and N and C:N ratios determined by conventional methods (Anderson and Ingram, 1993). The inoculums used were cattle manure CM (250 g in 1 l water) activated EM (100ml in 1 l water), a mixture of CM and EM (250 g CM and 100ml EM in 1 l water) with water as a control and 500 ml of each inoculum were added to the respective compost piles and coveredfor a period of 40 days with mixing at 10 day intervals. At 40 days samples were analysed for N and C: N ratios and the respective composts added to separate plots of 1 x 1m, replicated 4 times within a Randomized Block design. Uniform seeds of beans (Var. Top Crop) were planted at a spacing of 10 x 15 cm, 5 days after the addition of composts, and maintained organically, At the R1(flowering) stage, 4 plants were carefully uprooted, plant height recorded, nodule numbers counted and root length determined by the grid technique. Mycorrhizal infection was determined by the grid line intersect method as described by Ambler and Young (1977). Fresh pod yields were recorded and the data analyzedstatistically using a GLM procedure.

Results and Discussion

Legume green manure (Gliricidia) increased N contents and reduced the C: Nratios of preinoculated compost(Table 1), highlighting their value in composting when compared to non legume green manures. This is due to the greater N content in this material. The use of all components developed the best composts, highlighting the usefulness of material diversity in obtaining quality compost for organic farming

Tab. 1: N and C: N ratios of different compost materials (dry matter basis)

Composts / N mg.g-1 / C:N ratio
Straw + Gliricidia + Weeds (C1)* / 5.84 / 26.5
Straw + Tithonia + Weeds (C2) / 3.65 / 36.8
Straw + Gliricidia + + Tithonia + Weeds (C3) / 4.16 / 30.4
LSD (p=0.05) / 0.007 / 0.003

C1, C2 and C3 notations will be used in all tables to identify compost types

Microbial solutions (cattle manure or EM) increased N availability and lowered the C: N ratio of all composts, the use of a mixture had the most significant impact on these measured parameters (Table 2). EM had a greater beneficial effect in enhancing N availability of all composts, thus reducing the C: N ratios to a greater extent than CM. This clearly implied the importance of using an inoculant with known microbes for composting, rather than using ad hocfeedstock material, which could have different effects on the basis of microbes present.However, the use of inoculants such at EM must be carried out as per instructions to obtain the maximum beneficial effects.

Inoculation increased growth and yields of beans and the root microflora (Table 3). The impact of the three types of inoculum were EM + CM>EM >CM, highlighting the benefits of using both types of solutions. If one inoculum was to be used, EM which contains a known mixture of microbes had a more beneficial effect in enhancing growth, nodulation, mycorrhizal infection and yields of beans. The use of all plant material for compost also had a beneficial effect in terms of promoting yields, which is the most important factor in small holder farming systems and this could be attributed to the better quality of the material, especially when inoculated with EM and CM, which stimulates the roots and the rhizosphere.

Conclusions

Compost with legume leaves or preferably with a diverse range of material inoculated with EM and CM was of the highest quality and the most beneficial in terms of plant growth, yields and microbial populations of the roots. This clearly suggested the importance of using a range of inoculum and also the value of EM as a compost processing material. EM, which is now available in over 125 nations worldwide and made with the local microbes, would be a useful additive in composting within organic farming systems, as it is available at a relatively low cost. Thus tropical and even temperateorganic farming systems could easily develop good compost by using EM with other feedstock inoculum for obtaining quality compost for successful cropping.

Tab. 2: N and C:N ratios of composts at 40 days after inoculation (dry matter basis)

Inoculation / C1 Compost / C2 Compost / C3 Compost
N
mg.g-1 / C:N ratio / N
mg.g-1 / C:N ratio / N
mg.g-1 / C:N ratio
CM / 4.14 / 25.4 / 2.11 / 34.2 / 3.12 / 25.6
EM / 4.36 / 21.5 / 2.21 / 33.9 / 3.59 / 24.8
CM + EM / 4.99 / 20.8 / 2.65 / 30.6 / 4.01 / 20.5
Water / 2.42 / 26.8 / 1.42 / 35.8 / 2.24 / 29.5
LSD (P=0.05) / 0.24 / 0.05 / 0.33 / 0.02 / 0.18 / 0.01

LSD (P=0.05) for compost comparisons N = 1.04; C:N ratio = 0.13; Interaction Significant at P=0.05

References

Ambler, J.R. and Young, J.L. (1977). Techniques for determining root length infected by VA Mycorrhizas Soil Sci. Soc Am. J 41: 551 – 556.

Anderson, J M ., Ingram, J.S. (1993). Tropical soil biology and fertility. A handbook of methods. 2nd Ed. CAB International. Wallingford, U.K. 221p.

Diaz, L F (2007). Compost Science and Technology. Oxford. Elsevier, U.K 255p.

Gaskell, M., and Smith, R. (2007). N sources of organic vegetable crops. Horttech. 17: 431 – 441

Herencia, J.F., Ruiz-Porras, J.C., Melero, S., Garcia-Galavis, P.A., Morillo, E., Maqueda, C. (2007). Comparison between organic and mineral fertilization for soil fertility levels, crop macronutrient concentrations and yields. Agron, J. 99: 973 – 983.

Jenkins, T.A. and Daly, M (2005). Solid fermented material (Bokashi) as a biofertilizer for potting media using EM. Researching sustainable systems. Ed. Köpke, U. et al. ISOFAR, Adelaide:66 – 69.

Mupondi, L.T., Mnkeni, P.N., Brutsch, M.O. (2006). The effects of goat manure, sewage sludge and EM on the composting of pine bark. Compost Sci. Utilization 14: 201 – 210

Tab. 3: Growth, root microbial infection and yields of beans as affected by different composts and inoculations

Composts / Inoculum / Shoot height (cm)** / Total root length (cm) / Nodules
.plant-1 / %Root infection
(Mycorrhiza) / Yield.
g.plant-1
C1 / Cattle manure slurry (CM) / 25.6 / 258 / 16 / 22 / 421
Effective Microorganisms (EM) / 26.4 / 284 / 24 / 27 / 511
EM + CM / 30.5 / 324 / 35 / 31 / 567
Water / 21.5 / 205 / 10 / 12 / 224
C2 / Cattle manure slurry (CM) / 20.6 / 289 / 22 / 34 / 367
Effective Microorganisms (EM) / 22.6 / 314 / 31 / 36 / 451
EM + CM / 24.5 / 338 / 46 / 45 / 472
Water / 20.6 / 266 / 18 / 18 / 215
C3 / Cattle manure slurry (CM) / 26.6 / 315 / 26 / 32 / 494
Effective Microorganisms (EM) / 30.4 / 342 / 40 / 41 / 699
EM + CM / 32.5 / 390 / 51 / 47 / 781
Water / 36.2 / 284 / 42 / 20 / 267
LSD (p=0.05) / Compost / 0.004 / 0.014 / 0.009 / 0.021 / 0.018
Inoculum / 0.009 / 0.001 / 0.020 / 0.008 / 0.007
Interaction / * / * / NS / * / *

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[1]Faculty of Agriculture, University of Peradeniya, Sri Lanka (Email )